Tuning carrier density across Dirac point in epitaxial graphene on SiC by corona discharge

Abstract

We demonstrate reversible carrier density control across the Dirac point (Delta n similar to 10(13) cm(-2)) in epitaxial graphene on SiC (SiC/G) via high electrostatic potential gating with ions produced by corona discharge. The method is attractive for applications where graphene with a fixed carrier density is needed, such as quantum metrology, and more generally as a simple method of gating 2DEGs formed at semiconductor interfaces and in topological insulators.<p>Funding Agencies|Graphene Flagship [CNECT-ICT-604391]; Swedish Foundation for Strategic Research (SSF); Linnaeus Centre for Quantum Engineering; Knut and Allice Wallenberg Foundation; Chalmers AoA Nano; NMS (UK); EMRP project GraphOhm; EMRP within EURAMET; European Union</p

Physics of a disordered Dirac point in epitaxial graphene from temperature-dependent magnetotransport measurements

“…The as-grown samples have large uniform monolayer areas, where devices with an eight-leg Hall bar geometry of various sizes were fabricated using standard electron-beam lithography followed by O 2 plasma etching and large-area titanium-gold contacting. A nonvolatile polymer gating technique was used to control the carrier density in epitaxial graphene by room-temperature UV illumination [16] or corona discharge [17]. The polymer gates consist of bilayer polymer coating on top of the graphene Hall bars, forming SiC/graphene/polymer heterostructures.…”

“…We used two different techniques to reduce the relatively high initial electron density and tune the Fermi level to the vicinity of the Dirac point, where four-probe resistance maxima were observed: CD1 and CD2 were treated with multiple negative ion projections onto the bilayer polymer gate, produced by corona discharge using a piezo-activated antistatic gun [17], resulting in extremely low final electron densities of 1.2 and 1.3 × 10 10 cm −2 , respectively; UV1 was treated with deep UV illumination using a 248-nm mercury lamp [16] which eventually reduced the electron density to 8 × 10 10 cm −2 . As we will show below, these values should not be treated as the real electron densities, but merely are effective carrier densities, n eff , calculated from the low-field Hall coefficients at 1.4 K assuming a homogeneous landscape with a single type of charge carrier.…”

Magnetic field driven ambipolar quantum Hall effect in epitaxial graphene close to the charge neutrality point

“…Negative ions were produced by repeated corona discharges with a time interval of 17 s, following the method described in Ref. [19]. The distance between the sample and the corona source was 12 mm.…”

Encapsulation of graphene in Parylene

“…Epitaxial graphene on SiC can also be encapsulated from the top with PMMA, and the chargeneutrality point can be shifted to zero with UV light 17 or by using discharges. 18 In this paper we introduce graphene encapsulation in Parylene as a potentially scalable replacement for hBN. Parylene is an oxygen-free polymer with a dielectric constant of the same order as that of SiO 2 .…”